This invention relates to an improved method and product for surfacing and/or polishing lenses and the like. More particularly, this invention relates to a novel gel producing fining or polishing pad which considerably simplifies the process of fining and/or polishing lenses.
In general, the process for producing fine ground or polished surfaces on optical materials, such as for example on optical lenses, is much the same regardless of the type of fining or polishing medium employed, or the type of material being processed. In typical such operations, a fining or polishing pad is moved across the surface of the material to be processed, while either a slurry containing abrasive particles, or plain water, is directed in a stream between the pad and the surface to be processed.
One such prior art process is disclosed in U.S. Pat. No. 4,138,228, which teaches the use of a polishing pad having a water soluble, hydrophilic matrix containing unencapsulated abrasive particles that are rather weakly bonded to the matrix. This pad is used in conjunction with a constant stream of water, which assists in the release of polishing particles which are leached or torn from the pad matrix as the latter breaks down during use. In practice this pad has been found to be unsatisfactory because of the lack of contact between the released abrasive particles and the work.
U.S. Pat. No. 4,255,164 discloses a glass fining pad or sheet having a water insoluble, microcellular matrix containing abrasive fining particles. When the pad is used with an aqueous flow or stream its matrix breaks down and allegedly releases the fining particles at a controlled rate. While being effective for the grinding or fining stages of surfacing, this type of pad is not effective for polishing, even when using a polishing grade abrasive.
U.S. Pat. No. 4,576,612 discloses a polishing pad having a water soluble matrix containing polishing particles. A stream of water which is directed onto the interface between the pad and the work causes the exposed surface of the matrix slowly to dissolve thus slowly releasing polishing particles.
U.S. Pat. No. 3,042,509 also discloses a wax-like, polyethylene based polishing compound containing polishing particles, and adapted to be rubbed onto the surface of a buffing wheel or lap to provide both lubricating and polishing properties for the wheel or lap surface. The compound is water-soluble so that it can be washed off of the wheel after the buffing operation.
Still other such prior art processes showing desirability of directing a slurry or other liquid in a stream to the interface between the work and a grinding or polishing pad are disclosed in U.S. Pat. Nos. 3,921,344; 3,959,935; 3,522,680; 3,225,497; 3,128,580 and 2,886,923.
None of the above-noted patents, however, discloses a pad designed to produce an abrasive gel upon being wetted. Moreover these prior art processes involve several problems, including the following:
A. It is difficult to keep the abrasive particles suspended in the liquid slurry or stream; or in other words, to prevent the settling out of the particles. PA1 B. Large amounts of abrasive particles tend to stick to and to dry upon the processing equipment. PA1 C. Frequent repair and replacement of pumps, which are used to circulate the abrasive slurry, are necessary. PA1 D. It is extremely difficult to mix and control the concentration of the abrasive slurry.
One object of this invention, therefore, is to provide an improved fining or polishing process which eliminates the need for directing a stream of water or liquid slurry onto the work, thereby circumventing many of the problems associated with the previously mentioned processes.
To this end it is an object also to provide a novel fining or polishing pad which in the presence of a small amount of water forms a very viscous gel, which adheres both to the object being polished and to the pad substrate.
Still another object is to provide a novel water absorbent or adsorbent pad which, when wetted, makes all of its abrasive material instantly available for fining or polishing.
A further object of this invention is to provide a novel pad of the type described having an abrasive-containing matrix made from a polymer which can absorb and retain large amounts of water to enable formation of a long lasting gel.
Still another other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawing.